Cell Free Application: Characterization of Long Non-coding RNA Inhibition of Transcription

Long noncoding RNAs have been shown to regulate chromatin states, transcriptional activity and post transcriptional activity (1). Only a few studies have observed long non-coding RNAs modulating the translational process (2). The noncoding RNA BC200 has been shown to inhibit translation by interacting with the translation initiation factors, eIF4A and eIF4B.

To characterize how BC200 translational inhibition could be controlled,  a variety of RNAs were transcribed/translated in vitro using the TNT system (Cat. #L4610) from Promega. To each transcription/translation reaction, BC900 RNA, hnRNPE1 and hnRNE2 proteins were added. Inhibition of BC200 activity was noted when proteins were successful expressed (3).

Literature Cited

  1.  Sosinska, P et.al. (2015) Intraperitoneal invasiveness of ovarian cancer from the cellular and molecular perspective. Ginekol. Pol. 86, 782–86.
  2. Geisler, S. and Coller, J. (2013) RNA in unexpected places: long non-coding RNA functions in diverse cellular contexts. Nat.Rev. Mol. Cell. Bio. 14,699–12.
  3. Jang, S. et. al. (2017) Regulation of BC200 RNA-mediated translation inhibition by hnRNP E1 and E2. FEBS Letters. 591, 393–5.

Luciferase Immunoprecipitation System Assay (LIPS): Expression of Luciferase Antigen using TNT Transcription/Translation Kit

NanoLuc dual reporters

Illustration showing NanoLuc and firefly luciferase reporters.

The luciferase immunoprecipitation system (LIPS) assay is a liquid phase immunoassay allowing high-throughput serological screening of antigen-specific antibodies. The immunoassay involves quantitating serum antibodies by measuring luminescence emitted by the reporter enzyme Renilla luciferase (Rluc) fused to an antigen of interest. The Rluc-antigen fusion protein is recognized by antigen-specific antibodies, and antigen-antibody complexes are captured by protein A/G beads that recognize the Fc region of the IgG antibody (1).

In a recent publication (2), this assay was used to assess the presence of autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in patients with atrophic body gastritis and in controls. Continue reading

Cell Free Expression Application: In vitro degradation assay

A protein chain being produced from a ribosome.

A protein chain being produced from a ribosome.

Researchers and clinicians are fairly certain that all cervical cancers are caused by Human Papillomavirus (HPV) infections, and that HPV16 and HPV18 are responsible for about 70% of all cases. HPV16 and HPV18 have also been shown to cause almost half the vaginal, vulvar, and penile cancers, while about 85% of anal cancers are also caused by HPV16.

E6 is a potent oncogene of HR-HPVs, and its role in progression to malignancy continues to be explored. The E6 oncoprotein of HPV can promote viral DNA replication through several pathways. It forms a complex with human E3-ubiquitin ligase E6-associated protein (E6AP), which can in turn target the p53 tumor-suppressor protein, leading to its ubiquitin-mediated degradation. In particular, E6 from HR-HPVs can block apoptosis, activate telomerase, disrupt cell adhesion, polarity and epithelial differentiation, alter transcription and G-protein signaling, and reduce immune recognition of HPV-infected cells.

In a recent publication a new procedure generated a stable, unmutated HPV16 E6 protein (1). Continue reading

Protein:DNA Interactions—High-Throughput Analysis

Protein-DNA interactions are fundamental processes in gene regulation in a living cells. These interactions affect a wide variety of cellular processes including DNA replication, repair, and recombination. In vivo methods such as chromatin immunoprecipitation (1) and in vitro electrophoretic mobility shift assays (2) have been used for several years in the characterization of protein-DNA interactions. However, these methods lack the throughput required for answering genome-wide questions and do not measure absolute binding affinities. To address these issues a recent publication (3) presented a high-throughput micro fluidic platform for Quantitative Protein Interaction with DNA (QPID). QPID is an microfluidic-based assay that cam perform up to 4096 parallel measurements on a single device.

The basic elements of each experiment includes oligonucleotides that were synthesized and hybridized to a Cy5-labeled primer and extended using Klenow. All transcription factors that were evaluated contained a 3’HIS and 5’ cMyc tag and were expressed in rabbit reticulocyte coupled transcription and translation reaction (TNT® Promega). Expressed proteins are loaded onto to the QIPD device and immobilized. In the DNA binding assay the fluorescent DNA oligonucleotides are incubated with the immobilized transcription factors and fluorescent images taken. To validate this concept the binding of four different transcription factor complexes to 32 oligonucleotides at 32 different concentrations was characterized in a single experiment. In a second application, the binding of ATF1 and ATF3 to 128 different DNA sequences at different concentrations were analyzed on a single device.

Literature Cited

  1. Ren, B. et al. (2007) Genome-wide mapping of in vivo protein-DNA binding proteins. Science 316, 1497–502.
  2. Garner, M.M. (1981) A gel electrophoresis method for quantifying the binding of proteins to specific DNA regions. Nuc. Acids. Res. 9, 3047-60.
  3. Glick,Y et al. (2016) Integrated microfluidic approach for quantitative high throughput measurements of transcription factor binding affinities. Nuc. Acid Res. 44, e51.

Cell-free Expression: A System for Every Need

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Cell-free protein expression is a simplified and accelerated avenue for the transcription and/or translation of a specific protein in a quasi cell environment. An alternative to slower, more cumbersome cell-based methods, cell-free protein expression methods are simple and fast and can overcome toxicity and solubility issues sometimes experienced in traditional E. coli expression systems.

In his webinar, “In vitro, cell-free protein expression–How it helps speed up your research”, Gary Kobs offered an overview of the different cell-free expressions systems offered by Promega and highlighted what needs the different systems best address. He discussed different applications of cell-free expressed proteins and highlighted the combined uses of the HaloTag® Technology with cell-free protein expression. Continue reading

Compound Screening Using Cell-Free Protein Expression Systems

A protein chain being produced from a ribosome.

A protein chain being produced from a ribosome.

Both prokaryotic and eukaryotic cell-free protein expression systems have found great utility in efforts to screen organic compounds for inhibition of the basic cellular functions of transcription and translation, common targets for antibiotic compounds.

Cell-free systems can provide some advantages over cell-based systems for screening purposes. Cell-free systems allow exact manipulation of compound concentrations. This is an important parameter when evaluating the potential potency of the lead compound.

There is no need for cellular uptake to evaluate the effect of the compounds. While uptake evaluation is important for determining the eventual efficacy of the drug, it can unnecessarily eliminate valuable lead compounds in an initial screen. The interpretation of results in living cells is complicated by the large number of intertwined biochemical pathways and the ever-changing landscape of the growing cell. Cell-free systems allow the dissection of effects in a static system for simpler interpretation of results and the ability to specifically monitor individual processes such as transcription or translation. Individual targets not normally present, or found at low concentrations, can be added in controlled amounts.

The following references illustrate this application:

Cell-Free Protein Expression: Characterization of Plant Proteins

Cell free protein expression can be utilized for the analysis of: protein/protein interactions, protein nucleic acid interactions, analysis of post translational modifications and many other applications. The majority of these references are based on the characterization of mammalian proteins.
However there are several references using TNT-based systems (either rabbit reticulocyte lysate or wheat germ based) for the analysis of proteins from plants, examples include: Continue reading

Cell-Free Expression Applications: Characterization of Viral-Mediated Diseases

INFECTION IS BY TRANSCRIPTION OF THE VIRAL DNA INTO THE GENETIC MATERIAL OF THE HOST CELL, SO ANTIBODY TEST ING CAN DIAGNOSE AIDS. MORE SIGNIFICANTLY, IF THE PERCENTAGE OF LYMPHOCYTES THAT ARE CD4+ IS ABOVE 500 PER CUBIC MM THERE IS BETTER PROGNOSIS FOR TREATMENT. HERE THE VIRUS IS BUDDING FROM THE T CELL AS PART OF ITS PROLIFERATION AFTER INFECTING THE T CELL. AIDS VIRUS DIGITIZED TEM COLOR ENHANCED

The characterization of viral mediated diseases is critical to promote the overall welfare of humans or animals. Initial research focused on the interpretation the genomic content (i.e., DNA or RNA based) of the selected virus. The next step is to better understand the proteins that are encoded by this content and their interaction with the host proteome.
The following citations illustrate the use of cell-free protein expression to facilitate this research. Continue reading

Alternative Applications Using Cell-Free Protein Expression: #2

As noted in a previous posting the primary use of cell free expression as been the characterization of protein interaction. Due to the convenience of expressing functional protein in a few hours, cell-free expression is also a viable alternative to cell-based expression for other applications. Recent examples include:

Chloroplast import assay

Tanz, S. et al. (2009) Loss of the transit peptide and an increase in gene expression of an ancestral chloroplastic carbonic anhydrase were instrumental in the evolution of the cytosolic C4 carbonic anhydrase in Flaveria. Plant Physiology, 150, 1515–29

Carbonic anhydrase catalyzes the reversible hydration of CO2 and is involved in both C3 and C4 photosynthesis, however its role and intercellular and intracellular locations differ between C3 and C4 plants. Three different cDNA encoding distinct β-carbonic anhydrases were isolated from leaves of the C3 plant Flaveria pringle. To determine if either of the proteins encoded by the cDNA clones are targeted for chloroplasts, [35S]Met labeled proteins were expressed using cell free expression and subjected to chloroplast protein import analysis.

Translational regulation

Carra, S et al. (2009) HspB8 participates in protein quality control by a non-chaperone-like mechanism that requires eIF2{alpha} phosphorylation. J. Biol. Chem. 284, 5523–32.

The HspB8-Bag 3 protein complex suppresses mutated Huntington aggregation via autophagy and may involve translational arrest via eIF2 phosphorylation. To evaluate this theory, cell free expression was used to express a clone containing the Huntington exon 1 fragment in the presence of different amounts of recombinant HspB8 protein. To determine if HspB8 induces elF2(αlpha) phosphorylation, recombinant HspB8 was added (in addition to controls) and the extent of phosphor-elF2 levels were determined by Western blotting.

In vitro Compartmentalization

Chen, Y. et al. (2008) Cell-free selection of RNA-binding proteins using in vitro compartmentalization. Nuc. Acids. Res. 36, e128.

Using In vitro compartmentalization individual genes can be expressed in minute droplets of emulsified cell-free expression system. Formation of the droplet results in co-compartmentalization of the gene and its product, making it possible to select larger gene libraries compared to phage display. This reference illustrates a modification of this technique developed to link genotype and phenotype by fusing the target RNA binding protein to zinc finger proteins that bind to a cognate DNA sequence inserted upstream of the promoter.

Alternative Applications for Cell-Free Expression

proteinexpressionTwo of the most frequent applications that use cell-free expression are the characterization of protein:protein interactions and the characterization of protein:nucleic acid interactions. Due to the convenience of expressing functional protein in few hours, cell-free expression is also a viable alternative to cell-based expression for other applications. Recent examples include: Continue reading